Conventionally, a tire test for determining good or bad by measuring tire uniformity (uniformity of tire) and the like has been performed on tires as finished products. For example, in the case of performing a tire test on a tire for a passenger car, the tire uniformity is measured by the following procedure using a test apparatus as illustrated in Patent Reference 1 and the like.
That is, in the tire testing apparatus of Patent Reference 1, the tire flowing from the upstream of an inspection line is sandwiched by divided upper and lower rims, and the tire is inflated in a short time and fixed between the upper and lower rims. After that, by setting the internal pressure of the tire to a test pressure, the rotary drum is pressed against the tire held at the test pressure and is rotated normally or reversely to measure the tire uniformity.
When measuring the tire uniformity in this way, it is necessary to accurately grasp a relation between the pressing position of the rotary drum and the tire load (pressing load) generated at the pressing position, and to correctly generate the target pressing load (that is, a target tire load) on the tire. For this purpose, the tire testing apparatus is controlled using the relation existing between the pressing position of the rotary drum and the generated tire load to measure the tire uniformity.
For example, in Patent Reference 2, a tire testing apparatus is controlled, using a spring constant when assuming that a pressing position of a rotary drum and a tire load generated at the pressing position linearly change. That is, Patent Reference 2 discloses a method for measuring the relation between the pressing position and the generated tire load in advance, calculating the spring constant from the measured value, and controlling the tire load (pressing load) assuming that the calculated spring constant is constant.